Complex three-dimensional structures of 10- to 300-µm-diameter microchannels fabricated in a photocurable resin mix fluids more efficiently and in a smaller footprint than 2-D and 1-D devices, report researchers from the University of Illinois at Urbana-Champaign in the April issue of Nature Materials. They suggest that the devices may find use in biotechnology, chemistry and fluidic-based computing applications.To produce the structures, the scientists use an automated direct-write system to fabricate a 3-D layered scaffold pattern in fugitive organic ink. They infiltrate the pattern with an epoxy resin, remove the ink and produce square-spiral mixing towers by introducing the photocurable resin, which they expose in the desired pattern through photomasks. They used fluorescence microscopy to compare the mixing efficiency of the 3-D devices with 2-D and 1-D microchannel designs.